Manufacturing of organic electroluminescent (EL) devices uses a method of applying an organic EL ink into a film to form an organic functional layer. The organic EL ink and the organic EL devices including the organic EL ink will deteriorate over time. To deal with such deterioration, a variety of methods have been devised. For example, techniques are proposed in which ozone is focused as a cause to deteriorate organic EL ink, and an organic EL luminous layer is formed in a housing having an air atmosphere with an ozone concentration lower than that in the air (see PTL 1).